White Noise – A Warning

A number of parenting books suggest using white noise to help your baby to sleep. White noise is the background noise of machines. Some books will suggest vacuuming, running the washing machine, or even having a radio on in the baby’s bedroom with the tuning between stations, so that you can hear the soft buzzing. You can even buy CDs of white noise to play to your baby.

Before you choose white noise to settle your baby, please read the following extract from a book by a psychiatrist who studies the brain. He is talking about research done by a neuroscientist called Michael Merzenich into the increase in autism in our society.

One disturbing study showed that the closer children lived to the noisy airport in Frankfurt, Germany, the lower their intelligence was. A similar study, on children in public housing high-rises above the Dan Ryan Expressway in Chicago, found that the closer their floor was to the highway, the lower their intelligence. So Merzenich began wondering about the role of a new environmental risk factor that might affect everyone but have a more damaging effect on genetically predisposed [to autism] children: the continuous background noise from machines, sometimes called white noise. White noise consists of many frequencies and is very stimulating to the auditory cortex [of the brain].

“Infants are reared in continuously more noisy environments. There is always a din,” he says. White noise is everywhere now, coming from fans in our electronics, air conditioners, heaters and car engines. How would such noise affect the developing brain? Merzenich wondered.

To test this hypothesis, his group exposed rat pups to pulses of white noise throughout their critical period [of brain development during infancy] and found that the pups [brain] cortices were devastated.

“Every time you have a pulse,” Merzenich says, “you are exciting everything in the auditory cortex – every neuron.” So many neurons firing results in a massive BDNF [hormone] release. And as his model predicted, this exposure brings the critical period to a premature close. The animals are left with undifferentiated brain maps and utterly indiscriminate neurons that get turned on by any frequency.

Merzenich found that these rat pups, like autistic children, were predisposed to epilepsy, and exposing them to normal speech caused them to have epileptic fits… Merzenich now had his animal model for autism.

Recent brain scan studies now confirm that autistic children do indeed process sound in an abnormal way. Merzenich thinks that the undifferentiated cortex helps to explain why they have trouble learning, because a child with an undifferentiated cortex has a very difficult time paying attention. When asked to focus on one thing, these children experience booming, buzzing confusion – one reason autistic children often withdraw from the world and develop a shell. Merzenich thinks this same problem, in a milder form, may contribute to more common attention disorders.